The invention relates to a transportation system with a switching valve for selection of different transport paths. It can be applied to a system having a storage container from which goods are to be transported to one of a number of receiving containers connected to said storage container, the desired receiving container being switched in by means of said valve. It can also be applied to an ash feeding-out system in a combustion plant with combustion in a pressurized fluidized bed, usually called a PFBC plant. Applied to the latter system, it may be utilized for bypassing parts of an ash feeding-out system of the kind disclosed in more detail in U.S. patent application Ser. No. 563,427 filed Dec. 20, 1983, and corresponding to Swedish patent application No. 8205748-0. Such ash feeding-out systems comprise a number a series-connected tubes between which the ash-gas flow is transferred between an upstream tube and subsequent downstream tubes in a connecting chamber arranged at the ends of the tubes.
The invention aims to provide a pneumatic transportation plant with a switching possibility for selection of different transport paths by means of a valve having such a design that the risk of clogging, leading to stoppage, or the risk of rapid wear of the components included is reduced to the greatest possible extent. When applied to a PFBC plant, the purpose is also to be able to bypass parts of said ash feeding-out system in order to adapt the operating conditions therein with respect to a varying load. In this type of plants, the pressure and the ash quantity vary greatly in dependence on the load. An ash discharge device dimensioned for full load operation operates unsatisfactorily in partial load operation because the speed of transportation is so low that stoppage may occur. By shortening the transport path in the ash discharge device by bypassing certain parts, a smooth adaptation to partial load operation is made.